The current control of exhaust gas recirculation (EGR) during operation of an internal combustion engine, such as a diesel engine, of a vehicle relies on mass air flow (MAF) sensors in order to determine and regulate a quantity of recirculated exhaust gas. In this context, a flow of fresh air to the engine is regulated by setting a position of an EGR valve.
Documents DE 19628852 A1 and U.S. Pat. No. 5,520,161 describe a system for exhaust gas recirculation for a compression ignition engine and a method for controlling the exhaust gas recirculation in the compression ignition engine. In this context, a first pressure sensor is used for sensing an absolute gas pressure in an intake collecting line of the engine, a second pressure sensor is used for sensing an absolute gas pressure in an exhaust gas collecting line of the engine, and an engine rotational speed sensor, a fuel rate sensor, a temperature sensor in the intake collecting line, and further components are used for controlling a position of an exhaust gas recirculation valve.
Document U.S. Pat. No. 6,944,530 B2 discloses a system for exhaust gas recirculation, in which system exhaust gas from an exhaust gas manifold is conducted through a control valve and through a measuring nozzle before it reaches an inlet manifold. A pressure upstream of the nozzle and a correction pressure downstream of the nozzle are used to measure and control the exhaust gas flow.
Document U.S. Pat. No. 6,035,639 describes a method for estimating an inlet air flow into an internal combustion engine. Here, an amount of exhaust gas recirculation flow is determined as a function of an inlet manifold pressure, an outlet manifold pressure, a position of an exhaust gas recirculation valve, and a temperature of exhaust gas flowing through an exhaust gas recirculation system. The value of the inlet air flow is also used to control the position of the exhaust gas recirculation valve.
Document U.S. Pat. No. 6,098,602 describes an exhaust gas recirculation system for an internal combustion engine comprising an exhaust gas recirculation valve that is operated by a stepping motor. In particular, the control of the engine in order to achieve a desired exhaust gas recirculation mass flow rate is described.
However, the inventors herein have recognized potential issues with such systems. For example, the above mentioned systems and methods do not address effects such as MAF sensor drift, tolerances of components, and aging of the components, for example, which may influence a determination of an EGR flow rate. Therefore, with progressive aging of the vehicle, the efficiency of EGR control for reducing NOx emissions may be markedly reduced.
An advantage of the present disclosure is to make available a method and a device for predicting an exhaust gas recirculation rate of an internal combustion engine, wherein, in particular, aging processes and/or sensor differences are accounted for. In one example, the issues described above may be addressed by a system comprising an inlet system coupled to an internal combustion engine; an exhaust gas recirculation (EGR) valve coupled between an exhaust of the engine and the inlet system; and a device to predict an EGR rate based on a composition of gas in the inlet system and a position of the EGR valve. In this way, the exhaust gas recirculation rate may be accurately predicted without a MAF sensor.
As one example, the position of the EGR valve may be adjusted responsive to the predicted EGR rate differing from a desired EGR rate in order to achieve the desired EGR rate. Thus, the device for predicting the EGR rate may be used to generate feedback for accurate EGR control. As another example, the predicted EGR rate may be used to determine an EGR mass flow. Further still, the determined EGR mass flow may be used to determine a fresh air mass flow. Thus, the fresh air mass flow may be determined based on output of the device for predicting the EGR flow rate instead of using a dedicated air flow sensor, and degraded EGR control due to, for example, air flow sensor aging may be avoided.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.